Poor nutrition and weight loss are thought to be key to a recently described geriatric syndrome "failure to thrive" (FTT) - an incompletely understood process leading to impaired functional and health status in older adults. However, the relationships between poor nutrition, weight loss, and FTT: and the potential for reversibility is unclear. Previous studies, primarily in hospital and nursing home settings, indicate that involuntary weight loss is associated with adverse health outcomes. A preliminary study on veteran outpatients found that both involuntary and "voluntary" (by dieting) weight loss were similarly associated with increased morbidity and mortality. While presumably a marker of comorbid conditions, it may be that weight loss, per se, causes or exacerbates FTT by impairing immunity, reducing lean body mass and physical strength, and/or by other unknown mechanisms. A better understanding of the contribution of specific disease processes and psychosocial factors to weight loss and decreased functional status in the elderly would help to clarify these issues. Specific aims of this project are: 1) describe the incidence and clinical significant of weight loss in a community dwelling elderly population; 2) identify common causes and risk factors for weight loss and decreased functional status; 3) evaluate the clinical implications of involuntary versus voluntary weight loss; 4) identify possible mechanisms of FTT. The primary 4 year prospective study utilizing Senior Center attendees will collect data on patient sociodemographics, physiologic parameters (e.g., body weight and composition, insulin-like growth factor 1 levels, albumin, etc), and health and functional status. By delineating causes and effects of both voluntary and involuntary weight loss, this study will help to determine appropriate (and cost-effective) evaluations and interventions for elderly patients with weight loss. Multivariate analyses will also test the hypothesis that weight loss per se adversely affects health and functional status. A pilot study is planned to identify potential pathophysiologic mechanisms by which poor nutrition and weight loss contribute to FTT. Four elective surgical procedures will be evaluated as models for studying factors which influence or mediate the effects of acute stressful events on physiologic, functional and health status measures. By elucidating the causes and effects of weight loss, this project will help to identify interventions which may prevent or interrupt the cycle of disease and dysfunction associated with weight loss and failure to thrive.